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Precise Determination (precise + determination)
Selected AbstractsConjugated-Polymer/DNA Interpolyelectrolyte Complexes for Accurate DNA Concentration Determination,ADVANCED MATERIALS, Issue 7 2006W. Hong Precise determination of DNA concentration without the health risks of intercalating dyes is possible via the optical changes that arise from DNA-induced aggregation of cationic conjugated polyelectrolytes. Addition of DNA to a conjugated electrolyte containing two fluorophores results in aggregation and fluorescence quenching, inducing a measurable and quantifiable shift from blue- to green-light emission (see figure and inside cover). [source] Variation in 16S-23S rRNA intergenic spacer regions among Bacillus subtilis 168 isolatesMOLECULAR MICROBIOLOGY, Issue 1 2001Yevette J. Shaver The genome of the Bacillus subtilis 168-type strain contains 10 ribosomal RNA (rRNA) operons. In the intergenic spacer region (ISR) between the 16S and 23S rRNA genes, five rRNA operons, rrnI-H-G and rrnJ-W, lack a trinucleotide signature region. Precise determination of molecular weight (MW), using electrospray mass spectrometry (MS), of the polymerase chain reaction (PCR) products from a segment of the ISR from the 168-type strain and B. subtilis 168-like strain 23071 demonstrated 114 and 111 basepair (bp) PCR products (due to the presence or absence of the insert in the operons) as predicted from sequence. However, PCR of the ISR segment for five other B. subtilis 168 isolates generated only a 114 bp PCR product, suggesting the presence of the trinucleotide signature region in all rRNA operons for these strains. Additional genetic variability between the seven B. subtilis 168 isolates was demonstrated by restriction fragment length polymorphism (RFLP) of the rRNA operons, with three distinct patterns found upon Southern blot analysis. The 168-type strain and three others (23066, 23067, and 23071) exhibited the same Southern pattern. Thus, operon deletion is not responsible for the absence of a 111 bp product on MS analysis for strains 23066 and 23067. Restriction analysis confirmed the presence of the trinucleotide signature region in the ISR of all rRNA operons for five B. subtilis 168 isolates; sequencing of rrnW/H from a representative strain also upheld this finding. These results help provide a better understanding of variations in sequence, operon number and chromosomal organization, both within a genome and among isolates of B. subtilis subgroup 168. It is also hypothesized that the presence of the trinucleotide insert in certain rRNA operons may play a role in rRNA maturation and protein synthesis. [source] Laboratory Forum: Cavernous Nerve Injury Using Rodent Animal ModelsTHE JOURNAL OF SEXUAL MEDICINE, Issue 8 2008Onder Canguven ABSTRACT Introduction., With the advance of the "nerve sparing" technique in radical pelvic surgeries, medically unaided rates of normal erectile function following surgery have improved. Precise determinations of post-surgery erection recovery, however, continue to be problematic and rates of normal erectile function range from 9% to 86%. It is understood that injury to cavernous nerves (CNs) occurs despite modern modifications of the surgery, although the precise pathophysiologic mechanisms of surgical erectile dysfunction are not completely understood. Aim., To describe the experimental models of CN injury in small rodents, including both survival surgery (CN injury) and non-survival surgery (monitoring of intracavernosal pressure and arterial blood pressure) models. We also summarize studies on experimental procedures relating to these CN injury models and critique techniques according to their advantages and disadvantages. Main Outcome Measure., Data from a peer review literature search on the topic of CN injury in rodent models. Methods., A comprehensive review of the literature was performed using PubMed. "Cavernous nerve injury" and "animal model" were used as search terms, and a manual bibliographic review of cross-referenced items was performed. Results., Assorted molecular, morphological, and physiological changes are measurable after CN injury in rodent models. Conclusion., Various models of CN injury have been applied successfully and offer insights regarding erectile function recovery effects. Canguven O, and Burnett A. Cavernous nerve injury using rodent animal models. J Sex Med 2008;5:1776,1785. [source] Voltammetric Determination of ,-Tocopheryl Acetate in Pharmaceutical Dosage FormsELECTROANALYSIS, Issue 11 2004Slawomir Michalkiewicz Abstract A simple and rapid voltammetric method has been developed for the quantitative determination of ,-tocopheryl acetate (,-TOAc) in pharmaceutical preparations. Studies with linear scan (LSV), square-wave (SQWV) and differential pulse voltammetry (DPV) were carried out using platinum microelectrodes. A well-defined, irreversible oxidation wave/peak was obtained at 1.30,V (vs. Ag/AgCl reference electrode.) The use of SQWV or DPV technique provides a precise determination of ,-tocopheryl acetate using the multiple standard addition method. The statistical parameters and the recovery study data clearly indicate good reproducibility and accuracy of the method. Accuracy of the results assessed by recovery trials was found within the 99.3% to 103.5%, and 99.1% to 101.4%, for SQWV and DPV, respectively. The quantification limits for the both voltammetric techniques were found to be 6×10,5,M (SQWV) and 7×10,5,M (DPV). Analysis of the authentic samples containing ,-TOAc showed no interference with common additives and excipients, such as unsaturated fatty acids (co-formulated as glycerine esters) and vitamin A (as retinol or ,-carotene). The method proposed does not require any pretreatment of the pharmaceutical dosage forms. A gas chromatography determination of ,-TOAc in real samples was also performed for comparison. [source] The Relationship Between 27Al Quadrupolar Parameters and AlF63, Octahedron Connectivity in Crystalline and Glassy Fluoroaluminates,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2007Monique Body Abstract 27Al SATRAS and MQ-MAS spectra were recorded for eight crystalline compounds, from the CaF2,AlF3 and BaF2,AlF3 binary and BaF2,CaF2,AlF3 ternary systems, and four glass compositions with different CaF2/BaF2/AlF3 contents. For the crystalline phases, the reconstruction of the spectra leads to the precise determination of the NMR parameters. For the glassy phases, the 27Al SATRAS spectra have been reconstructed using quadrupolar parameter distributions. The main finding of this study is the dependence of the quadrupolar frequency on the type of AlF63, octahedron connectivity. For crystalline phases the experimental ,Q values range between 75 kHz and 510 kHz for structures built up from isolated octahedra, and are between 560 kHz and 1250 kHz for structures built up from isolated chains of cis -connected octahedra, and are between 1530 kHz and 1580 kHz for structures built up from isolated chains of trans -connected octahedra. In the glassy phases the maximum of the quadrupolar frequency distribution shifts toward larger values and its width increases with increasing AlF3 content, and subsequently with the number of connected octahedra. The range of the ,Q values seems to indicate that when the octahedra are connected, cis connections occur most frequently. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] "PHYBAL" a Short-Time Procedure for a Reliable Fatigue Life CalculationADVANCED ENGINEERING MATERIALS, Issue 4 2010Peter Starke Abstract The reliable calculation of the fatigue life of high-strength steels and components requires the systematic investigation of the cyclic deformation behaviour and the comprehensive evaluation of proceeding fatigue damage. Besides mechanical stress-strain hysteresis measurements, temperature and electrical resistance measurements were used for the detailed characterisation of the fatigue behaviour of the steel SAE 4140 in one quenched and tempered, one normalised, one bainitic and one martensitic condition. To guarantee optimal operation conditions the new fatigue life calculation method "PHYBAL" on the basis of generalised Morrow and Basquin equations was developed. It is a short-time procedure which requires the data of only three fatigue tests for a rapid and nevertheless precise determination of S-N (Woehler) curves. Consequently, "PHYBAL" provides the opportunity to reduce significantly experimental time and costs compared to conventional test methods. [source] Cytochrome b559 content in isolated photosystem II reaction center preparationsFEBS JOURNAL, Issue 10 2003Inmaculada Yruela The cytochrome b559 content was examined in five types of isolated photosystem II D1-D2-cytochrome b559 reaction center preparations containing either five or six chlorophylls per reaction center. The reaction center complexes were obtained following isolation procedures that differed in chromatographic column material, washing buffer composition and detergent concentration. Two different types of cytochrome b559 assays were performed. The absolute heme content in each preparation was obtained using the oxidized-minus-reduced difference extinction coefficient of cytochrome b559 at 559 nm. The relative amount of D1 and cytochrome b559,-subunit polypeptide was also calculated for each preparation from immunoblots obtained using antibodies raised against the two polypeptides. The results indicate that the cytochrome b559 heme content in photosystem II reaction center complexes can vary with the isolation procedure, but the variation of the cytochrome b559,-subunit/D1 polypeptide ratio was even greater. This variation was not found in the PSII-enriched membrane fragments used as the RC-isolation starting material, as different batches of membranes obtained from spinach harvested at different seasons of the year or those from sugar beets grown in a chamber under controlled environmental conditions lack variation in their ,-subunit/D1 polypeptide ratio. A precise determination of the ratio using an RC1-control sample calibration curve gave a ratio of 1.25 cytochrome b559,-subunit per 1.0 D1 polypeptide in photosystem II membranes. We conclude that the variations found in the reaction center preparations were due to the different procedures used to isolate and purify the different reaction center complexes. [source] High-resolution synchrotron radiation studies on natural and thermally annealed scleractinian coral biomineralsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2007J. Stolarski The structural phase transition from aragonite to calcite in biogenic samples extracted from the skeletons of selected scleractinian corals has been studied by synchrotron radiation diffraction. Biogenic aragonite samples were extracted en bloc without pulverization from two ecologically different scleractinian taxa: Desmophyllum (deep-water, solitary and azooxanthellate) and Favia (shallow-water, colonial, zooxanthellate). It was found that natural (not pulverized) samples contribute to narrow Bragg peaks with ,d/d values as low as 1 × 10,3, which allows the exploitation of the high resolution of synchrotron radiation diffraction. A precise determination of the lattice parameters of biogenic scleractinian coral aragonite shows the same type of changes of the a, b, c lattice parameter ratios as that reported for aragonite extracted from other invertebrates [Pokroy, Quintana, Caspi, Berner & Zolotoyabko (2004). Nat. Mater.3, 900,902]. It is believed that the crystal structure of biogenic samples is influenced by interactions with organic molecules that are initially present in the biomineralization hydrogel. The calcite phase obtained by annealing the coral samples has a considerably different unit-cell volume and lattice parameter ratio c/a as compared with reference geological calcite and annealed synthetic aragonite. The internal strain in the calcite structure obtained by thermal annealing of the biomineral samples is about two times larger than that found in the natural aragonite structure. This effect is observed despite slow heating and cooling of the sample. [source] Hildebrand and Hansen solubility parameters from Molecular Dynamics with applications to electronic nose polymer sensorsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 15 2004M. Belmares Abstract We introduce the Cohesive Energy Density (CED) method, a multiple sampling Molecular Dynamics computer simulation procedure that may offer higher consistency in the estimation of Hildebrand and Hansen solubility parameters. The use of a multiple sampling technique, combined with a simple but consistent molecular force field and quantum mechanically determined atomic charges, allows for the precise determination of solubility parameters in a systematic way (, = 0.4 hildebrands). The CED method yields first-principles Hildebrand parameter predictions in good agreement with experiment [root-mean-square (rms) = 1.1 hildebrands]. We apply the CED method to model the Caltech electronic nose, an array of 20 polymer sensors. Sensors are built with conducting leads connected through thin-film polymers loaded with carbon black. Odorant detection relies on a change in electric resistivity of the polymer film as function of the amount of swelling caused by the odorant compound. The amount of swelling depends upon the chemical composition of the polymer and the odorant molecule. The pattern is unique, and unambiguously identifies the compound. Experimentally determined changes in relative resistivity of seven polymer sensors upon exposure to 24 solvent vapors were modeled with the CED estimated Hansen solubility components. Predictions of polymer sensor responses result in Pearson R2 coefficients between 0.82 and 0.99. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1814,1826, 2004 [source] Discovery of a short orbital period in the Supergiant Fast X-ray Transient IGR J16479,4514MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2009Chetana Jain ABSTRACT We report here the discovery of a 3.32 d orbital period in the Supergiant Fast X-ray Transient (SFXT) source IGR J16479,4514. Using the long-term light curve of this source obtained with Swift Burst Alert Telescope (BAT) in the energy range of 15,50 keV, we have clearly detected an orbital modulation including a full eclipse of duration ,0.6 d. In the hard X-ray band of the BAT instrument, the eclipse ingress and egress are rapid. We have also used the long-term light curve obtained with the Rossi X-ray Timing Explorer (RXTE) All Sky Monitor (ASM) in the energy range of 1.5,12 keV. Taken independently, the detection of orbital modulation in the RXTE,ASM light curve is not significant. However, considering a clear detection of orbital modulation in the BAT light curve, we have used the ASM light curve for a more precise determination of the orbital period. IGR J16479,4514 has the shortest orbital period among the three SFXTs with measured/known orbital period. We discuss the implication of a short orbital period with the various mechanisms proposed to explain the transient nature of this class of sources. [source] Determination of the mobility ratio in InSb at the temperature of the conductivity type conversionPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2005K. SomogyiArticle first published online: 22 FEB 200 Abstract The temperature dependence of magneto-transport in bulk p-type InSb was investigated, and a special approach was applied for the precise determination of the temperature dependence. Such measurements also allow the determination of the mobility ratio (b) which is known to be large in InSb. Although this type of investigation is standard, in this work an improved method of carrying out temperature-dependent Hall measurements is reported and improved calculations for the determination of large b values in InSb are presented. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spectral Acquisition and Calibration Techniques for the Measurement of Radiative Flux Incident upon PropellantPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 1 2003Michael Abstract A technique for the absolute calibration of a time-resolved spectrographic system has been developed at QinetiQ, specifically designed to be relevant to spectral acquisition from within the interior of translucent gun-propellant samples. The technique has shown itself to be particularly useful in the realm of propellant ignition as it allows for the precise determination of the moment that propellant combustion processes begin, as well as measuring the incident radiative flux leading up to ignition. Scope exists to extend its use for high-pressure measurements of the incident radiative flux during both conventional propellant burn and high-powered electrothermal-chemical (ETC) discharges. This paper sets out to describe both the technique and some of the pitfalls encountered during the development of the technique. The use of this technique in some of the experimental work performed at QinetiQ, including the results of measurements that compare the incident radiative flux with propellant ignition during both ETC discharges and conventional gunpowder burn, have been published separately; references for this experimental work are given in this paper. [source] Order,disorder transition in monoclinic sulfur: a precise structural study by high-resolution neutron powder diffractionACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2006W. I. F. David High-resolution neutron powder diffraction has been used in order to characterize the order,disorder transition in monoclinic cyclo-octasulphur. Rapid data collection and the novel use of geometrically constrained refinements has enabled a direct and precise determination of the order parameter, based on molecular site occupancies, to be made. The transition is critical and continuous; with a transition temperature, Tc = 198.4,(3),K, and a critical exponent, , = 0.28,(3), which is indicative of three-dimensional ordering. Difficulties encountered as a consequence of the low thermal conductivity of the sample are discussed. [source] Pseudomerohedrally twinned monoclinic structure of unfolded `free' nonactin: comparative analysis of its large conformational change upon encapsulation of alkali metal ionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009Ilia A. Guzei The title compound, C40H64O12, crystallizes in a pseudomerohedrally twinned primitive monoclinic cell with similar contributions of the two twin components. There are two symmetry-independent half-molecules of nonactin in the asymmetric unit. Each molecule has a pseudo- S4 symmetry and resides on a crystallographic twofold axis; the axes pass through the molecular center of mass and are perpendicular to the plane of the macrocycle. The literature description of the room-temperature structure of nonactin as an order,disorder structure in an orthorhombic unit cell is corrected. We report a low-temperature high-precision ordered structure of `free' nonactin that allowed for the first time precise determination of its bond distances and angles. It possesses an unfolded and more planar geometry than its complexes with encapsulated Na+, K+, Cs+, Ca2+ or NH4+ cations that exhibit more isometric overall conformations. [source] New classification and basic stellar parameters of SU EquuleiASTRONOMISCHE NACHRICHTEN, Issue 7 2009O. Behre Abstract The variable star SU Equulei was classified as a close binary with an eclipse light curve previously categorized as WUMa type. The aim of this paper is a review of this old classification on the basis of new observations and a new determination of variable star ephemeris as well as the determination of SU Equ spectral type and distance. New photometric observations in different colours allow a precise determination of the period of variability and yield more accurate light curves allowing a re-classification of the type of variability. We find the best period of variability to be half the old value. The shape of the light curve is inconsistent with an eclipse curve but consistent with an RR Lyrae type c classification. From the B, V, and R colours we deduce a new spectral classification. SU Equulei is an RRc Lyrae type variable of spectral class A8 at a distance of ,12.4 kpc instead of a late-type eclipsing binary (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A robust method to determine global distribution of atmospheric boundary layer top from COSMIC GPS RO measurementsATMOSPHERIC SCIENCE LETTERS, Issue 3 2010M. V. Ratnam Abstract In this study, we introduce a robust method for precise determination of atmospheric boundary layer (ABL) top from COSMIC global positioning system radio occultation measurements. We apply a wavelet covariance transform to compute the convolution of COSMIC-observed bending angle/refractivity profile with a Haar function and use the maximum covariance to identify the ABL top, making detection of even small transitions possible. Results obtained were compared with radiosonde N profiles for verification of the ABL top. This procedure developed was used to study the global distribution of ABL top with special reference to the inter-tropical convergence zone. Copyright © 2010 Royal Meteorological Society [source] Determination of Biomass Composition of Catharanthusroseus Hairy Roots for Metabolic Flux AnalysisBIOTECHNOLOGY PROGRESS, Issue 6 2006Ganesh Sriram Metabolic flux analysis is a powerful diagnostic tool in metabolic engineering, and determination of biomass composition is indispensable to accurate flux evaluation. We report the elemental and biomolecular composition of Catharanthus roseus hairy roots, a pharmaceutically significant plant system and an important metabolic engineering target. The molecular formula of the organic material in the hairy roots was C12.0H22.7N0.4O7.6 during mid-exponential growth. The abundances of lipids, lignin, cellulose, hemicellulose, starch, protein, proteinogenic amino acids, mineral ash, and moisture in the biomass were quantified. Analysis of water-soluble components of the biomass with 1-D 13C and 2-D [1H,1H] correlation (COSY) NMR spectroscopy revealed that the water-soluble components were composed almost entirely of ,-glucans. Agropine, a frequently reported hairy root biomass component, was not detected. Our measurements of the biomass components quantified 83.6 ± 9.3% (w/w) of the biomass. Together with previously reported abundances of indole alkaloids, we accounted for at least 85.9 ± 11.6% (w/w) of the carbon in the biomass, which enabled the precise determination of 12 biomass synthesis fluxes. [source] Modeling of Monolith-Supported Affinity ChromatographyBIOTECHNOLOGY PROGRESS, Issue 3 2004Francisco J. Montes Sanchez Ceramic monoliths have been used successfully as active support for affinity chromatography ( 1). A mathematical model was developed to simulate the adsorption-elution experimental behavior of asparaginase in an agarose-coated monolith support. The computer-based model allows precise determination of experimental parameters. Because of the simple geometry of ceramic monoliths used as support, the mathematical model can be used to design adsorption/elution cycles for the large throughput separation of biomolecules. [source] | |||||||||||||||||||